A detailed investigation of the rate enhancements observed in the hydrolysis of o-carboxy substituted benzal chlorides in dioxane-water mixtures will be continued. Principal mechanistic tools to be used are alpha, beta, and solvent isotope effects in conjunction with the addition of salts such as LIClO 4 and LiCl. We have recently developed the use of solvent isotope effects such that under at least some conditions this mechanistic tool is capable of providing valuable insight into the nature of the rate-limiting step. We intend to further refine this technique. Specific substrates to be investigated are o-carboxydiphenyl dichloromomethane, 1-(o-carboxyphenyl)-2, 2-dichloroethane. BIBLIOGRAPHIC REFERENCES: Cyclohexadienyl Cations. VII. Methyl Group Isotope Effects in the Dienane-Phenol Rearrangement. V.P. Vitullo and E.A. Logue, J. Amer. Chem. Soc., 98,000 (1976). Deuterium Isotope Effects in the Solvolysis of Benzal Chlorides. I. alpha-Deuterum Isotope Effects and Salt Effects in the Solvolysis of p-Methoxybenzal Chloride in Dioxane-Water Mixtures, V.P. Vitullo and F.P. Wilgis, J. Amer. Chem. Soc., 97, 458 (1975).